The present invention relates to a device for stepless alteration of the seat depth of a car seat cushion, and more particularly to a device comprising a variable-pressure air cushion which is arranged, on the front side of the seat cushion, between a padded rest and a supporting surface. As a result of a pressure increase in the air cushion, the associated region of the padded rest is deployed. The seat surface is lengthened in the process, and a cover which covers over the padded rest consequently is lengthened by expansion of its fixed end region.
A device for altering the seat depth is described in EP 0 204 443 A2. The rectangular air cushion underside rests on a supporting surface which, when the air cushion unfolds, bends downwardly about a defined pivot axis, so that a relatively large volume of air is necessary for inflating the air cushion. An encircling fastening border encloses the air cushion which, with the unfolding of the air cushion, results in a hump-like elevation which falls away towards the side borders of the seat cushion. A side support which has considerable influence on the seat comfort is thus not provided.
An object of the present invention is to configure the air cushion and to integrate it into the seat structure such that, with a small inflation volume, in addition to the increase in the seat depth, there is also comfortable side support in the lengthening region.
This object has been achieved according to the present invention by providing that the air cushion is approximately U-shaped with legs thereof, oriented in a direction of a rear edge of the seat cushion, bearing on a side support which terminates towards the front side of the seat cushion and is formed by dimensionally stable supporting surface.
The extremely dimensionally stable supporting surface hardly yields at all when there is a build-up of pressure in the air cushion. As a result, the change in volume of the air cushion is virtually fully converted into an alteration of the seat depth. The air volume which is necessary to produce the maximum possible lengthening of the seat depth is thus relatively small and can be achieved in an extremely short period of time. The changeable-volume legs of the air cushion are assigned to the supporting surface such that they only appear at the beginning of the inflation operation. That is, the legs bring about a stepless transition from the unalterable side support to the changeable-height side support.
A reduction of pressure in the air cushion rapidly results in a reduction in volume if, on its base sides, the air cushion has lugs which are integrally formed on at least in certain areas, are connected, on the upper side, to the supporting surface by retaining means penetrating into the supporting surface, and are fixed, on the underside, on the substructure of the supporting surface with the interposition of at least one elastic strip.
In a currently preferred embodiment of the present invention, the supporting surface is formed by the upper side of a mat which covers over the spring arrangement and consists, for example, of rubberized hair.